This invention relates to an infinitely variable cone pulley transmission including two pulleys, one mounted on a driving shaft and the other mounted on a driven shaft which is parallel-spaced from the driving shaft. An endless transmission member, such as a drive belt is trained about the two pulleys. Each pulley is formed of a pair of conical pulley discs, one of which is axially displaceable on its respective shaft and is at least indirectly torque-transmittingly connected therewith. Each such axially displaceable pulley disc forms a power cylinder which rotates in unison with the respective shaft. With the power cylinder there is associated a piston which is affixed to the shaft and to which there is applied pressurized hydraulic fluid for setting and maintaining the transmission ratio by means of a slide valve having four control sections. The slidable control valve is connected, for example, with the intermediary of a setting lever, with one of the axially displaceable pulley discs. The two other pulley discs are axially immovably and torque-transmittingly mounted on the driving and driven shafts. For the load-dependent generation of pressing forces there is provided a sensor on at least one shaft adjacent the fixed pulley disc for sensing the torque transmitted at that location. To the sensor there is admitted hydraulic fluid at a pressure which prevails in the cylinder-and-piston assembly on its own shaft or the other shaft and which is necessary for setting and maintaining the desired transmission ratio. The sensor, by means of a torque-dependent relative motion between two valve components of a valve, generates a torque-dependent hydraulic pressure and determines the required load-dependent hydraulic pressing force. Further, the sensor is formed as a torque-dependent pressing device which operates with face-to-face arranged camming faces and rolling bodies disposed therebetween. The sensor has a first ring which is remote from the fixed pulley disc and which carries one half of the curved pressing faces. The first ring is axially immobilized to the shaft for unison rotation therewith.
Cone pulley transmissions as outlined above are disclosed in German Laid-Open Application (Offenlegungsschrift) No. 2,846,580. The embodiments disclosed therein show--and this equally applies to the invention to be described as the specification progresses--that the torque sensor may be arranged in different ways dependent upon specific requirements demanded of the transmission. The usual case which will be considered in connection with the invention to be described below, without however, limiting the invention thereto, resides in that the torque sensor is mounted on the driving shaft of the transmission and is exposed to the fluid pressure prevailing in the piston-and-cylinder assembly associated with the driven side of the transmission. According to another structural possibility the sensor is mounted on the driven shaft and is exposed to the hydraulic pressure prevailing at the driven side or the sensor is mounted on the driving shaft and is exposed to the hydraulic pressure prevailing at the driving side. Or, it is also feasible to mount a separate torque sensor on each shaft and to expose each torque sensor to the hydraulic pressure associated with its own shaft. In the latter case, however, under the conditions disclosed in the above-noted Laid-Open Application, one of the torque sensors is always idle.
The known torque sensor is in particular so structured that the fixed pulley disc associated therewith constitutes or actuates one of the valve parts for generating the load-dependent pressing force. As a result of such an arrangement, the fixed pulley disc is, transversely to the direction of run of the endless transmission member (drive belt or chain) displaced back and forth corresponding to the amount serving for the valve control. This leads to a corresponding offsetting of the track of the endless transmission member which, dependent upon the mode of application and load of the transmission may be disadvantageous and thus undesirable. Then, the bearing base for the fixed pulley disc also does not have to be as wide as in the known case.
Furthermore, the known torque sensor has a relatively large spatial requirement in the axial direction of the transmission and has numerous individual components.